JP2000158328A - System and method for electro-chemical and mechanical polishing for magnetic board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve surface finished flatness after a polishing process, by polishing a medium in the presence of an electric field slurry by energizing a board, chemically and mechanically polishing a surface of the board, generating current between the board and a conductive member, and electrically polishing the board surface. SOLUTION: A rigid board 20 is polished by rotating and/or vibrating it in a state that it is pressed onto an abrasive pad 22 supported on a static abrasive platen 24. The board 20 vibrates and rotates at a place where slurry provided from a supply source 28 exists. This slurry is discharged on an interface between the abrasive pad 22 and the board 20 through one or more nozzle 30, and simultaneously a current supply voltage is impressed from a power supply 32 to a gap between the abrasive platen 24 and the board 20. The power supply 32 may be direct current(DC) voltage source, and at this case, preferably, the board 20 is a positive electrode (positive terminal) and the abrasive platen 24 is a negative electrode (negative terminal).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates generally to the manufacture of rotating magnetic disk substrates in data processing systems and magnetic storage memory systems for data storage systems, and more particularly to magnetic disk memories. To a method and apparatus for polishing a surface of a rigid substrate disk as provided.

[0002]

2. Description of the Related Art Magnetic disk memories used in data processing and data storage systems generally comprise a plurality of rigid magnetic media disks stacked on a spindle assembly and rotating at high speed. Each disk is divided into a plurality of concentric tracks, and each track becomes an addressable area of the magnetic memory. The tracks are accessed via a magnetic head flying over a thin layer of air over the surface of the disk. Typically, the disc has two sides, with the head accessing each side.

A magnetic medium of a magnetic disk memory generally has a rigid disk substrate made of a high-purity alloy. After the surface of the substrate is finished to provide a uniformly smooth surface, it is plated with a thin layer of a material such as nickel, typically to a thickness of less than about one thousandth of an inch. You. The surface is then mirror polished, configured to provide a circumferential minimal groove, and then coated with a thin film of a magnetic material such as a platinum alloy or a tantalum-cobalt alloy.

Because of the small dimensional characteristics, tight tolerances, and ultra-thin layers of material on the substrate, it is important that the substrate and coating be smoothed and sufficiently polished to a mirror finish prior to application of the magnetic film layer. It is. Currently required tolerances for surface finish are 3 to 5 angstroms in average roughness. It is very likely that these tolerances will be tightened in the future. To achieve that level of finishing,
Typically, a series of polishing, cleaning, and polishing steps are required. The polishing process of the substrate surface may be performed by a circumferential polishing machine, an orbital motion polishing machine, or a planetary motion.
on) can be performed using polishing equipment. Circumferential polishers typically secure the substrate on the shaft end so that the substrate is rotated, while the linear tape and the substrate are mechanically pressed against the surface by a load roller. Engage the front and rear surfaces. The tape may be comprised of a well-known material comprising a layered woven polymer type or grown polymer type abrasive having a mylar tape substrate or a plurality of other materials. The tape abrasive is passed over a roller, which is pressed against the substrate surface. Typically, during the polishing process, a liquefied abrasive contained in the slurry is applied between the substrate and the polishing pad / tape combination to achieve the desired polishing operation and to smooth and smooth the substrate surface. Cooling. Orbital polishers are somewhat similar in that they polish the entire surface all the time, while circumferential polishers typically polish only a small fraction of the entire surface at all times. Inside the orbiting polisher, the substrate is held in place by a substrate carrier and pressed against a polishing pad supported on a polishing platen. The substrate carrier and the substrate rotate in orbital motion on the polishing pad where the liquid slurry is present. Typically, as in a circumferential polisher, an orbital polisher utilizes a liquid slurry that is abrasive and has a specific chemical polishing composition to facilitate the orbital polishing process. The process of chemical mechanical polishing of metal surfaces has been a rather time consuming process when using conventional polishing equipment.

[0005] Other forms of metal finishing methods are known, such as electrochemical etching or electrochemical finishing of conductive metal parts. Electrochemical finishing is typically applied to metal parts having irregular surfaces or metal parts that are not conveniently finished using a mechanical finishing process. Electrochemical finishing has been used, for example, to remove nicks from metal surfaces. Another specific application is, for example, the step of etching a cavity line in a barrel that must have a pitch that varies from the breech to the muzzle of the barrel.

[0006]

Although electrochemical processes allow for relatively high metal removal rates, current electrochemical methods provide a method for rotating magnetic storage memories while providing tight tolerance characteristics. Achieving the required type of smooth polished surface finish, on the other hand, lacks adequate process control to achieve relatively high material removal rates.

Accordingly, it is an object of the present invention to provide a process for finishing a rigid alloy type substrate for spinning magnetic storage memory that provides rapid removal of the alloy while providing tight and tight tolerance control over the surface finish of the substrate. It is to provide.

[0008]

SUMMARY OF THE INVENTION An apparatus for polishing a substrate used in the magnetic recording and storage system of the present invention comprises a polishing medium, means for moving the substrate to polish the medium relative to each other, and Means for energizing and polishing the medium together in the presence of the electrolytic slurry to chemically and mechanically polish the surface of the substrate, and generating an electric current between the substrate and the conductive member, A voltage source for electrically polishing the substrate surface, thereby achieving the above object.

[0009] The voltage source may include one of a DC voltage source and an AC high frequency voltage source.

The conductive member is stationary and connected to the voltage source, the substrate is movable by the moving means, and the apparatus slidably engages the moving means to move the substrate to the voltage source. An electrical contact for connecting to a source may be further provided.

The conductive member may include a plate mounted on the urging means so as to press the polishing medium against the substrate surface.

The movement means may rotate the substrate with respect to the plate, the plate being reproducible and shaped to provide a uniform current density on the surface of the substrate.

The plate may be wedge-shaped and all points on the substrate may be dimensioned such that a uniform current flows for a given period.

The polishing medium comprises a linear tape, and the biasing means comprises means for biasing a conductive member to engage the tape and press the tape against the surface of the substrate; The movement means may comprise means for rotating the substrate with respect to the tape.

[0015] The tape may be conductive, the electrolytic slurry may be conductive, and current may flow between the substrate and the conductive member via the tape.

The electrolytic slurry comprises an acid selected from the group consisting of sulfuric acid, chromic acid and orthophosphoric acid, ammonium sulfate, potassium chloride, potassium permanganate,
And a salt selected from the group consisting of nickel sulfate.

[0017] The substrate surface may be made of metal, and the slurry may be a sludge slurry containing a saturated solution of the metal.

The voltage source comprises an adjustable constant DC power supply;
The substrate may be connected to a positive terminal of the power supply, and the conductive member may be connected to a negative terminal power supply.

[0019] The voltage source may include means for adjusting the current in response to a computer control signal.

[0020] The polishing medium may comprise a linear tape, and the biasing means may comprise a roller engaging the tape, and means for pressing the roller and the tape against the surface of the substrate.

The roller may include the conductive member, the roller may be formed of a conductive material, and may be rotatably supported on a conductive shaft by a conductive bearing.

The conductive member may include an electrode disposed between the tape and the substrate surface, wherein the electrode engages the tape and is disposed in the flow of the electrolytic slurry. Good.

An apparatus for polishing a substrate used in a magnetic recording system according to the present invention comprises: means for rotating the substrate; means for advancing a linear polishing tape on both sides of the substrate; Means for mechanically polishing the surface by urging the polishing tape, and means for introducing an electrolytic slurry between the substrate and the polishing tape,
Voltage source means for supplying a voltage between the substrate and the electrode so that a current flows between the substrate and the electrode via the electrolytic slurry, thereby achieving the above object.

[0024] The tape may be conductive, the electrodes positioned to engage the tape, and current may flow between the substrate and the electrodes through the tape.

[0025] The electrode may include plates disposed on both sides of the substrate, and the biasing means may include means for pressing the plates together to press the tape against the surface of the substrate.

[0026] The voltage supply means may comprise a DC constant current control source, the tape being porous, allowing current to flow between the plate and the substrate through the tape.

The means for supplying a power supply voltage may include an AC constant current source.

Cooling the substrate and the rotating means,
A cooling unit for maintaining the temperature of the substrate and the rotating unit within a predetermined temperature range may be further provided.

[0029] The rotating means may include a rotating spindle, and the cooling means may include means for directing a cooling liquid onto the spindle and the substrate.

The voltage supply means includes a first power supply and a second power supply.
Power supply, each power supply is connected to one of the plates and the substrate rotating means, each of the power supplies can be independently controlled, and controls the current to each surface of the substrate. Good.

[0031] The power supply may comprise an AC source having means for adjusting the current in response to a computer control signal.

[0032] The plate may be shaped and dimensioned to provide a uniform predetermined current density across the surface of the substrate.

An apparatus for polishing a substrate used in the magnetic recording system of the present invention is an orbital motion polisher, which comprises a fixed polishing platen and a substrate carrier movable with respect to the fixed platen. Means for biasing the substrate into engagement with a polishing medium positioned on the stationary polishing platen, and means for moving the substrate in orbital motion on the polishing medium. An orbital motion polishing machine having: a means for introducing an electrolytic conductive slurry between the substrate and the polishing medium; and a voltage source connected to the polishing platen and the substrate carrier, wherein A current flows between the polishing platen and the surface of the substrate simultaneously with a chemical mechanical polishing step of the substrate surface for relative movement between the substrate and the polishing medium. And a voltage source which is adapted to electropolishing, thereby the objective described above being achieved.

[0034] The voltage source may include an AC constant-amplitude current source, and means for controlling the current source to supply a predetermined current between the substrate and the platen.

[0035] The AC source may include means for adjusting the current in response to a computer control signal.

The AC constant current source is from 1 kHz to 50 MHz.
It may have an output frequency in the range of z.

The method of polishing a substrate used in the magnetic recording system of the present invention comprises the steps of providing a polishing medium and pressing the substrate while energizing the substrate and the medium together in the presence of an electrolytic slurry. Exercising with respect to the polishing medium,
Chemically and mechanically polishing the surface of the substrate, and removing a material from the substrate surface while allowing current to flow through the slurry between the substrate and the conductive member; Electropolishing said substrate surface while said surface is being chemically and mechanically polished, thereby achieving said object.

The means for causing the current to flow may include the step of causing a uniform current density to flow between the substrate surface and the conductive member.

[0039] Preferably, the polishing medium comprises a first linear tape and a second linear tape having an abrasive coating thereon, the tape being disposed on both sides of the substrate and moving on the side of the substrate surface. Wherein said tape is biased by an interacting plate that is biased together to engage said substrate surface, allowing said current to flow, between each of said plates and said rotating substrate. The method includes a step of applying a voltage.

The voltage may include an AC constant-amplitude current source that is controlled to generate a predetermined current.

The method may further include the step of cooling the substrate during polishing to maintain the temperature substantially constant.

The present invention provides a method and apparatus system for electrochemically mechanically polishing an alloy-type substrate, whereby:
It provides a highly polished and smooth surface suitable as a base layer on which a magnetic thin film layer can be deposited, thus forming a composite magnetic disk medium for computer data storage.

More specifically, the present invention employs an electropolishing process for a substrate simultaneously with a chemical polishing process and a mechanical polishing process, wherein a voltage is applied between a rotating or orbiting substrate and an electrode. On the other hand, the substrate and the electrode are sealed in a conductive electrolytic slurry.

More specifically, the present invention accomplishes polishing by applying a current supply voltage between a moving rigid substrate and an electrode. The current supply voltage may be any one of a direct current (DC) power supply voltage preferably accompanied by constant current control or an alternating current (AC) power supply voltage. When using DC, it is preferred that the metal substrate be the anode or positive terminal and the polishing plate be the cathode or negative terminal. When an AC type power supply voltage is employed, the AC cycle of the power supply voltage is such that the substrate and the polishing plate alternately become both the anode and the cathode. A DC bias may be added to the AC voltage to ensure that the substrate remains at a positive voltage with respect to the cathode. The present invention applies a voltage between a moving substrate and a relatively stationary polishing plate or platen that supports a polishing medium, such as a linear tape or pad, while providing a high pressure polishing force. By adjusting the current density, the rate of metal removal from the substrate can be tightly controlled.

Polishing of an alloy type substrate used to form a magnetic storage medium is performed by subjecting the substrate to a chemical mechanical polishing operation in the presence of a conductive electrolyte and applying direct current (DC) or high frequency alternating current (DC). AC) so that one of them flows between the substrate and the electrode type platen via the conductive electrolyte,
This is done by removing material from the surface of the substrate in a controlled operation. Combined electro-chemical-mechanical polishing is performed on both circumferential and orbital polishing machines, and can use both DC and AC power supplies, each with a constant amplitude current control source It is.

[0046]

DETAILED DESCRIPTION OF THE INVENTION The present invention is particularly well adapted to the fine polishing process of alloy-type rigid substrates that receive magnetic films and are used as magnetic media in hard substrate drives in computer data processing systems. Explained in context. However, it will be understood that this is only an illustration of one application of the invention.

In summary, the basic principle underlying the present invention is to combine an electropolishing process with a chemical-mechanical polishing mechanism to accelerate the polishing process and improve the smoothness of the surface finish after the polishing process. . FIG. 1 shows a first embodiment of the present invention.
The principle is illustrated in the embodiment.

As shown in the figure, a rigid substrate 20, which typically takes the form of a disk and may be made of aluminum or an aluminum-magnesium alloy, is pressed onto a polishing pad 22 supported on a stationary polishing plastic template 24. In this state, the substrate may be polished by rotating and / or vibrating the substrate. The substrate 20 is the source 2
8 vibrates or rotates where the slurry obtained is present, and this slurry is caused by one or more nozzles 30 (only one is illustrated in the figure) at the interface between the polishing pad 22 and the substrate 20. At the same time, the power supply 32 applies a current supply voltage between the polishing platen 24 and the substrate 20. The power supply may be a direct current (DC) voltage source, in which case the substrate is preferably an anode (positive terminal) and the polishing platen 24 is preferably a cathode (negative terminal). DC is preferably a constant current supply in the range of 0.01 to 20 amps / in 2. For the two-sided process, it is preferable to use a constant current supply for each side, as described below. In the alternative, power supply 32 may be an AC voltage source that provides high frequency AC energy. AC
If a power supply is used, for example, 1 kHz to 50 MH
frequency between z and 0.01 to 20.0 amps /
A supply current density in the range of square inches may be employed. The slurry from the source 28 is preferably an electrolytically mixed polishing slurry compound, and the mechanism includes a non-movable polishing pad 22.
And the substrate 2 against the relatively stationary polishing platen 24
It is preferable to apply a high pressure polishing force to 0. Pressures on the order of 1 to 25 pounds per square inch (PSI) may be employed. Preferably, the substrate moves at a speed on the order of 200 mm / sec to 3000 mm / sec with respect to the immovable polishing pad and the relatively stationary platen 24.

FIG. 1 illustrates an orbiting or planetary polishing apparatus, and FIG. 2 illustrates a circumferential polishing apparatus according to another embodiment of the present invention. As shown in FIG. 2, the rigid substrate 40 is rotatable about a spindle shaft 42, while the moving linear tape 44 is
Is pressed against the surface of the substrate. The polishing slurry from the source 48 may be discharged by one or more distributors 50 into the space between the substrate surface and the polishing tape 44. At the same time, an electropolishing current is supplied between the substrate 40 and the electrode 54 by the voltage applied from the power source 52,
4 is preferably positioned in contact with the surface of the polishing tape 44 and is located in the slurry discharged by one of the distributors 50. As with the apparatus of FIG. 1, the power supply 52 may be either a DC power supply voltage or an AC power supply voltage, preferably with constant current control. When the power supply is a DC power supply voltage, the cathode (negative terminal) may be connected to the electrode 54, and the anode or positive terminal is connected to the spindle shaft 42 and the substrate. Further, the slurry from the source 48 is preferably conductive and produces an electrical current at the point of contact between the electrode 54 and the surface of the substrate 40 with the roller 46.

As shown in FIG. 2, the electrode 54 is
An arrangement located in the slurry between the substrate 4 and the substrate is useful, where the polishing tape is non-porous and non-conductive like Mylar. The conductive slurry flowing between the tape and the surface of the substrate 40 along the surface of the tape 44 on the side of the electrode 54 allows current to flow at the point of contact between the tape and the substrate surface. The slurry preferably includes a highly conductive electrolyte in the abrasive mixture to minimize resistance to electrical current. Further, the conductivity of the slurry mixture is preferably such that it provides a relatively low resistance even at a 2: 1 dilution with deionized water. The resistance of the slurry can be changed not only by changing the distance from the electrode 54 to the contact area between the tape 44 and the substrate surface 40, but also by changing its conductivity. This distance is preferably as small as possible.

In the electrochemical mechanical polishing process of the present invention, two solutions can be used. These are sludge solutions and non-sludge solutions. The sludge solution is a saturated solution of the metal to be polished, for example nickel. The metal salt formed as a by-product of the electropolishing operation does not dissolve in the saturated electrolyte and forms sludge, which is formed at the bottom of an electrolyte capture tank (not shown) that captures the electrolyte flowing on the side of the substrate. Settles. Non-sludge solutions are unsaturated and dissolve metal salts. The first of a class of solutions is preferably used in a prior art electropolishing mechanism, since the steady state process is optimized with a substantially permanent electrolyte. However, in the present invention, the expiration date of the electrolytic solution is not a factor, and the steady process is achieved by continuously supplying fresh slurry. Therefore, any type of slurry may be employed, but a saturated electrolyte is preferred.

However, the slurry should be optimized for prior art abrasive mechanical polishing operations and then for electropolishing operations. The electropolishing process requirements are high conductivity and preferably saturation of the nickel salt (to polish a nickel-plated substrate). To achieve high conductivity, acids such as sulfuric acid, chromic acid, orthophosphoric acid and the like can be added in percentages and weights on the order of 3% to 6%. These acids may be used alone or in combination with other substances that improve conductivity, such as, for example, salts such as ammonium sulfate, potassium chloride, potassium permanganate, and nickel sulfate. I just need. In addition, slurries that promote the anodic membrane are highly desirable.

The circumferential polishing apparatus illustrated in FIG. 2 uses the separation electrode 54 when the polishing tape 44 is non-porous like Mylar tape. In this case, the roller 46 is electrically insulated from the rest of the device. However, if the tape is perforated and therefore able to pass conductive electrolyte, or if the power source 52 is an AC power source, the back surface of the polishing tape itself, as shown in dashed lines in FIG. Can be connected to a power supply. This can be achieved by employing a roller formed as shown in FIG. 3, which is connected to a power supply using an electrically insulating L-shaped bracket 60, for example, ceramic. The resulting conductive shaft 62 is supported. The roller 46 may comprise a cylindrical roller surrounded by a thick wall of a conductive material such as aluminum or stainless steel, as shown, rotatably supported on a shaft 62 by a pair of bearings 64. Is done.
Bearings 64 are either grease-free bearings or bearings that employ conductive grease to provide electrical contact and current between shaft 62 and rollers 46. Washers 66 and fasteners 68 secure rollers 46 on the shaft.

The roller 46 is just one form of polishing plate that can be employed in the circumferential polishing apparatus of the present invention. Another specific example will be briefly described. The invention places great restrictions on the cathode or polishing plate, instead of having very few materials on the substrate (anode) to be polished. The material of the polishing plate is preferably such as aluminum or stainless steel, which avoids contamination of the polishing process. In addition, the size and placement of the polishing plate are important parameters because they affect the resistance of the electropolishing mechanism. The resistance depends in part on the distance between the substrate (anode) and the polishing plate or cathode. The placement of the polishing plate depends on the type of polishing medium used in the process. As described above, for the polishing tape with a Mylar substrate, the cathode, that is, the electrode 54 as shown in FIG. 2, needs to be installed on the front surface of the tape. In this case, the distance between the cathode or electrode 54 and the footprint of the roller on the substrate is very important. In order to minimize resistance, it is desirable that the cathode be located as close as possible to the point of contact. The resistance is not only a function of the distance between the electrode and the contact point as determined by the roller 46, but also
As will be described in more detail shortly, it is also a function of the footprint area of the moisturizing surface. The resistance R of the slurry is a function of the area A of the footprint of the cathode, plus the conductivity C of the slurry and the distance L from the anode (substrate) to the cathode.
Is also a function of

The slurry resistance is expressed as follows. R = (1 / C) (L / A)

Therefore, reducing the resistance in the slurry is made possible by increasing its conductivity, reducing the distance L between the anode and the cathode, and further increasing the contact area between the cathode and the anode. .

As will be described in more detail below, the electrical contact between the substrate and the power supply is made by means of a rotating spindle shaft 42 that holds and rotates the substrate 40 and a rotating member that is well known to those skilled in the art. This may be achieved by providing sliding electrical contact between the provision of a slip ring, a brush, or other mechanism such as a conductive liquid.

One of the reasons for minimizing the resistance is to minimize the resistance heating of the substrate during the electropolishing operation. It is desirable to maintain the spindle holding the substrate at a predetermined constant temperature to prevent the spindle and the substrate from becoming misaligned due to thermal deformation. Because the present invention allows a wide range of electrolytes to be employed, and allows for wide variations in processing parameters, under certain conditions the slurry resistance can be as large as, for example, 10 ohms. And the current can be made 10 amps. This is 10
It corresponds to a power of 00 watts and a voltage source of 100 volts, but very high. A more realistic resistance value for the expected condition is on the order of 3 ohms, and the current may be as little as 1 amp, which provides 3 watts of power. However, to accommodate a wide range of possible parameters, it is desirable to provide a system that cools and controls the temperature of the spindle and dish during operation.
A preferred embodiment of the circumferential polishing apparatus according to the present invention comprises:
Such a fluid cooling mechanism is employed, as described below.

A preferred embodiment of the circumferential polishing apparatus according to the present invention will be described below. The circumferential polishing device is Ru
U.S. Pat. No. 5,099,615, issued Mar. 31, 1992 to U.S. Pat.
US Patent No. 4,96, issued October 23, 990
Any modified version of the circumferential polishing apparatus disclosed in U.S. Pat. No. 4,242 may be used, and both of the above patents are assigned to the assignee of the present invention, the disclosures of which are incorporated herein by reference. ing. A preferred circumferential polishing apparatus may employ a linear polishing tape that is moved over rollers that are pressed into engagement with both sides of the rotating substrate. The apparatus of the above patent performs a chemical mechanical polishing operation, but does not incorporate an electropolishing process. However, the present invention modifies the prior art circumferential polishing apparatus to include an electropolishing step in a manner described below.

FIG. 4 is a front view of the modified circumferential polishing apparatus 100 according to the first embodiment of the present invention, and FIG. 5 is a rear view thereof. As shown, the apparatus includes a pair of axisymmetric tape transport assemblies that operate in concert to simultaneously polish the front and rear surfaces of the rotating rigid substrate 102. Each of the assemblies includes an abrasive linear tape or abrasive media 106, which may be comprised of an abrasive material such as, for example, aluminum oxide or silicon carbide incorporated into a binder system and coated on a flexible Mylar substrate. The tape 106 is a supply reel 108
Is wound around a lower turning roller 114 across a pair of rollers 110 and a tape guide 112. The tape is then wound on a take-up reel 118 around another pair of rollers 116. The take-up reel may be rotated by a conventional motor (not shown), and appropriate tension may be maintained on the tape by rollers 110 and 116 and maintained by a tension control mechanism (not shown) on supply reel 108.

In close proximity to the substrate 102, the tape 106 can be pressed against the surface of the substrate by a polishing plate 120 connected to a movable block assembly 122. The movable block assembly comprises a movable pulley and cable arrangement 12 of the type described in the aforementioned U.S. Pat. No. 4,964,242.
6 (see FIG. 5). The pulley and cable mechanism presses the polishing tape into engagement with the substrate surface such that the polishing plates 120 disposed on both sides of the substrate 102 are urged against the surface of the substrate as the substrate rotates. The polishing tape is moved on the side of the rotating substrate by a tape transport assembly. As best illustrated in FIGS. 6A and 7A, the polishing plate 120 need only have a generally triangular wedge or trapezoidal shape, and the polishing plate can be used with respect to the surface of the substrate by the polishing plate. When the tape is biased, engages the tape and guides it past the side of the polishing plate 120;
What is necessary is just to have a pair of projection guide rod 130. The polishing plate is preferably easily renewable and replaceable, in addition to allowing differently shaped plates to be used, as well as allowing the plate to be replaced when worn.

As shown in FIG. 7A, the footprint 132 of the polishing plate on the surface of the substrate is trapezoidal or wedge-shaped, with a wide footprint at the outer periphery of the substrate and toward the central opening 134 of the substrate. The wedge portion is tapered. The above is the preferable shape of the polishing plate. As briefly described below, when the substrate rotates on the side of the polishing plate, a current flows from the polishing plate 120 to the substrate 102 via the polishing tape. It is desirable that the current density per unit time flowing between the polishing plate and the substrate be equal at each radius of the surface of the substrate. Since the outer periphery of the substrate rotates at a greater angular velocity than the inner portion adjacent the central opening 134, the dimensions of the footprint 132 at the outer peripheral edge of the substrate can be selected with respect to the circumferential length of the footprint of the inner opening 134, and the current The density should be approximately uniform throughout the substrate surface. This is desirable to ensure uniform removal of metal across the surface of the substrate.

FIG. 7B illustrates another configuration of a polishing plate footprint 140 that can be used in place of the polishing plate 120 to achieve a uniform current density. As shown by footprint 140, the polishing plate may have a central V-shaped cut 142, and a pair of triangular contacts 144 may be provided as shown. The dimensions of the polishing plate with footprint 140 may be such that each contact provides a uniform current density across the surface of the substrate, as described in connection with polishing plate 120.

FIG. 7C illustrates another footprint 148, such as provided by a drum roller as shown in FIG. The footprint provides a circumferential dimension whose radius is constant over the surface of the substrate. This latter configuration does not produce as beneficial results as those provided utilizing the polishing plate described in connection with FIGS. 7A and 7B, but the rollers still produce acceptable results, Can be used.

Referring again to FIGS. 4, 5, 8 and 9, the substrate 102 may be coupled to the rotating spindle 150 by a collet 152 (see FIG. 6A). The collet is stretched in the manner described below to form the inner opening 1 of the substrate.
34 frictionally engages and holds the substrate on the spindle. US Patent No. 5,560,62 assigned to the assignee of the present invention.
No. 4 describes a disc clamp collet system. Further, the spindle is supported in a spindle housing 154 and can be rotated by a drive mechanism comprising a motor 156 and a drive belt 158. The drive belt may extend around the enlarged hub portion 160 on the spindle (see FIG. 9). As the motor 156 rotates, the drive belt 158 moves the spindle shaft 15
0 is rotated in the spindle housing 154. As a result, the substrate rotates between the two polishing plates 120,
At this time, the plate urges the polishing tape 106 into contact with the front and rear surfaces of the rotating substrate.

FIG. 9 is a vertical sectional view of the spindle assembly illustrating the operation of the collet 152. As shown in FIG. As shown, a longitudinally extending rod 164 is connected at its forward end to a collet 152 and at its opposite end to the pneumatic cylinder 1.
68. When the pneumatic cylinder is activated, the rod 164 may move within the longitudinal bore of the spindle, causing the collet to expand and contract. When extended, the collet engages the substrate surface in the central opening 134 and holds the substrate firmly on the spindle.

In order to pass current through the polishing plate via the substrate 102, electrical contacts must be made using the substrate. This provides sliding electrical contact to the spindle assembly 150, as best illustrated in FIGS.
The assembly can be formed from a metal conductor such as stainless steel or aluminum and rotatably supported by a spindle housing 154 on an electrically insulating block 170. Insulation block 170 may be formed, for example, of ceramic or other electrical insulator to support spindle housing 154, which then mounts spindle assembly 15
0 may be rotatably supported. Alternatively, both insulating block 170 and spindle housing 154 may be integrally formed from an insulating material that allows the spindle assembly to rotate freely within the housing. Electrical contact to the spindle assembly 172 is provided by a brush assembly shown in more detail in FIG. The brush assembly may be any commercially available unit and may include a carbon brush 174 that contacts the periphery of a portion 176 of the spindle assembly as it rotates within the spindle housing 154. As will be described, the conductor 178 electrically connects the brush assembly and the substrate 102 to a current source voltage supply via a spindle assembly.

The polishing apparatus 100 also includes a slurry transport system 180 best illustrated in FIG. 6A. As shown, the slurry transport system may include a pair of semi-cylindrical slurry distribution members 182 connected to the mounting member 184, and semi-cylindrical slurry distributors may be positioned on opposite sides of the substrate 102. The semi-cylindrical distributor may be hollow, and the slurry may be supplied via the slurry transport tape 186. The slurry is made up of a plurality of small openings 1 on the distributor surface.
Exiting the distributor through 88 may be guided to the surface of substrate 102 by a plurality of circumferentially extending grooves 190 formed along the length of distribution member 182. The slurry supplied to each member 182 exits the small opening 188, and the rotating substrate 102
Into the front and rear surfaces of the vehicle.

During operation, spindle and substrate temperatures may increase due to resistive heating. Substrate 102
To cool the spindle assembly and the spindle assembly, a cooling assembly 190 may be provided as illustrated in FIGS. 4 and 6A to 6B. As shown in FIG. 6B, the cooling assembly 190 may include a manifold having a longitudinally extending perforation 192 connected to a pair of nozzles 194. The piercing 192 pierces the fluid and the nozzle 194
Connected to a supply tube 196 for supplying the air to the supply line. The fluid may be, for example, water or cooling air, the nozzle 1
It flows out of 94 and impinges on the surface of the rotating substrate and the rotating spindle. This removes heat and controls the temperature of the spindle assembly and the substrate to avoid misalignment due to thermal effects and consequent defects in the polishing process of the substrate surface.

FIG. 8 is a rear view of a portion of a polishing apparatus illustrating the manner in which current can be supplied to polishing plate 120 and substrate 102. The bracket 60 on which the plate 120 is mounted is made of an electrically insulating material such as ceramic or any other non-conductive material that can be machined and made to maintain tight tolerances. As shown, the present invention preferably uses two voltage sources 200, which, as described above, preferably have a D current with constant current control.
It can be either a C voltage source or an AC voltage source. FIG.
One side of each of the voltage sources 200 is commonly connected to a brush assembly 172, as shown in FIG.
6 to provide electrical contact. The other side of the two voltage sources is a polishing plate 120 arranged on both sides of the substrate 102.
Connected to each other. 2 for 2 polishing plates
The use of a separate voltage source is advantageous in that it allows for independent control of the current flowing through each polishing plate, which provides tight control over the polishing operation for the following reasons: This is because the current difference between the two polishing plates can be offset. A single current supply is also available and may provide economic benefits.

The range and capacity of the power supply is programmable via a remote control computer (not shown), allowing operation over a wide range of conditions. As indicated above, the present invention is operable with a variety of different materials and can use a variety of different slurry compounds and a variety of different current densities. Constant current power supplies with adjustable current capacities in the range of 0 to 10 amps are suitable for multiple configurations and devices that differ from most applications.

When using a DC supply voltage, utilizing the polishing plate approach illustrated in FIGS. 2-8 requires that the tape be conductive. This is also true for the polishing pad used with the orbiting polisher of the present invention shown in FIG. 12 to conduct current from the cathode plate to the anode substrate, as described below. Non-conductive tapes and pads, such as Mylar base tape, require separate electrodes and arrangements as illustrated in FIG. 2 when using a DC power supply voltage. In this method, the electrode is placed in contact with the slurry electrolyte so that the current path between the cathode (electrode) and the substrate passes through the electrolyte. In this case, the direction of rotation of the substrate is important. It is advantageous to rotate the substrate in a direction that forms a liquid pool between the substrate and the tape. If the polishing plate is used as a cathode and as a means for biasing the tape into contact with the substrate, the tape is preferably made conductive. This can be accomplished by using a perforated tape, such as a woven tape, through which the electrolyte passes so that current can flow between the cathodic polishing plate and the anode substrate. Alternatively, the tape with a mylar substrate (insulator) may be made conductive by arranging a plurality of small holes through the mylar substrate. The holes can be randomly distributed in the tape, and the size and pattern of the holes are chosen so that they are not compatible with the polishing process, but provide sufficient passage for the electrolyte to match the required flow. obtain. Tapes with conductive substrates may also be used and are highly desirable. Such tapes are available on the market and can be made by embedding metal threads within a woven tape or by adhering a homogeneous distribution of a mixture of metal particles within a Mylar tape.
When a conductive tape is used, the electrode that contacts the tape is
Rather than placing an electrode between the tape and the substrate as illustrated in FIG. 2, it can be located at any convenient location along the base of the tape. However, for the reasons discussed above, it is preferred to use a polishing plate configured and dimensioned to ensure uniform current density across the surface of the substrate.

When using an AC voltage, conductive tape and electrolyte are desirable but not required. The reason is that the non-conductive tape and / or the non-conductive electrolyte form a capacitor through which the AC current from the AC voltage source can pass. FIG. 11 illustrates a preferred form of the computer controlled AC constant current source 220. As shown, the current source may comprise an AC oscillator 222, which may be an adjustable constant amplitude high frequency oscillator. The output from the oscillator is provided to a first operational amplifier (OP AMP) 224, whose output typically provides a sinusoidal voltage to a current sensing resistor R1 having a value on the order of 0.01 ohms. The current through the current sensing resistor may be sensed by a second operational amplifier 226, which amplifies the voltage and provides it to the input of automatic gain control operational amplifier 228. As shown for the electropolishing process, the current through the current sensing resistor R1 is also provided to the substrate 102. The output of automatic gain control operational amplifier 228 is fed back to the inverting input of operational amplifier 224 to complete the feedback loop through operational amplifier 226 and automatic gain control operational amplifier 228. This makes it possible to control the output of the power operational amplifier 224 to supply a constant current to the substrate.

The output of the operational amplifier 226 is also provided to a diode 230 and further to a voltage divider formed by resistors R2 and R3. The voltage is filtered by capacitor C1 and provided as a control input to automatic gain control operational amplifier 228. Operational amplifier 2
28 is also a digital-analog converter (D / AC)
Receiving a reference input generated by H.232, the converter can be controlled by a digital input signal from a remote control computer (not shown). The DC reference signal from the digital-to-analog converter 232 is
Compared to the gain modified DC signal obtained via 30, this diode filters the high frequency AC signal of the power operational amplifier 224 by a DC filter which is filtered by a low pass filter (represented by resistor R1 and capacitor C1) To voltage and then to the power operational amplifier 2
Provides a DC voltage that corresponds to the 24 high frequency AC signals and is a ratio-metric to it, which in turn is the automatic gain control input of the automatic gain control operational amplifier 228. Is fed back to the gain control input terminal. Due to the AC signal rectification and filtering effects, the gain of operational amplifier 228 is correspondingly adjusted so that the feedback signal matches the reference signal. This in turn adjusts the feedback signal to operational amplifier 224, and thus
To provide a constant current to the substrate 102 independent of the voltage required to achieve the desired computer commanded current. The cathode of the polishing apparatus 234, shown as a block diagram in FIG. 11, may be grounded, as illustrated. By properly adjusting the computer input to the digital-to-analog converter, the desired current for the electropolishing operation can be controlled and controlled as a function of time according to substrate finish requirements, as well as established and maintained. obtain.

FIG. 12 shows an application example of the present invention to an orbital motion polishing apparatus. In contrast to a circumferential polisher, an orbiting polisher polishes only one surface of a substrate at a time with a planetary motion on a polishing pad supported on a polishing platen. FIG.
2, a polishing pad 250 of a suitable abrasive material
May be supported on a fixed stationary platen 252 that is electrically grounded. The substrate 102 may be supported in a substrate carrier 254 that is connected to a suitable orbiting mechanism (not shown). While the carrier is orbiting, the carrier presses the substrate against the polishing pad 250. As shown in FIG. 12, the substrate is contained in a substrate carrier 254 by a cylindrical electrode 260 in a substrate carrier 254.
This cylindrical electrode engages the substrate at its central opening 134 (see FIG. 7A) to secure the substrate on the plate 258. Electrical contact between the constant current AC current source and the substrate may be via a cylindrical electrode 260, as shown in FIG.

The orbital motion polisher of FIG. 12 employs an ion polishing current through an electrolyte polishing slurry compound between the polishing platen and the substrate while allowing a defined orbital motion to be applied to the substrate. The substrate is preferably an anode (for a DC power supply voltage, preferably with constant current control). Electrical contact with the substrate allows high current densities to be employed for electropolishing operations. When using AC power, AC frequencies over a wide operating range may be used, for example from 1 kHz to 50 MHz depending on the desired electropolishing process. Current densities ranging from 0.01 to 20.0 amps per square inch may be used. During the polishing operation, the substrate is, for example, 1 to 2
What is necessary is just to press against a polishing pad and a platen using pressure in the range of 5 PSI.

While the above refers to preferred embodiments of the present invention, it is understood that the scope of those embodiments should, on the spirit of the invention, not depart from the principles set forth in the appended claims. It will be apparent to those skilled in the art that modifications can be made.

[0078]

The system for polishing a substrate used in the magnetic recording and storage system of the present invention combines an electropolishing process with a chemical-mechanical polishing process to provide a process that is approximately one-half of the prior art chemical-mechanical polishing process. It provides a very efficient high speed polishing that provides tighter control over the quality of the polishing surface while allowing for improvements that are 2 to 8 times faster.

The present invention allows metal removal rates in excess of, for example, 200 angstroms per second while
Provides an average surface roughness lower than 10 Angstroms root mean square (RMS), thereby allowing a highly polished mirror finish. As a result, the present invention allows for substantially higher production rates for alloy substrates for spinning magnetic storage memories with tight control over surface quality.

Further, as indicated above, the present invention can be employed with a wide variety of different alloy substrate materials and a wide variety of different processing parameters, depending on the requirements. This makes the present invention very advantageous for applications other than the manufacture of magnetic substrate media.

[Brief description of the drawings]

FIG. 1 is a diagram of a first embodiment of an electrochemical mechanical device for polishing a rigid substrate, illustrating the principles of the present invention.

FIG. 2 is a diagram of a circumferential electrochemical mechanical polishing apparatus according to the present invention.

FIG. 3 is an exploded partial cross-sectional perspective view of a conductive roller that can be employed in the circumferential polishing apparatus of FIG. 2;

FIG. 4 is a front view of a portion of a circumferential electrochemical mechanical polishing apparatus according to the present invention.

FIG. 5 is a rear view of the device of FIG. 4 with parts of the device omitted for clarity to help better understand important features of the device.

FIG. 6A is an enlarged perspective view of a portion of the apparatus of FIG. 4, illustrating key features of the electrochemical mechanical polishing apparatus.

FIG. 6B is a cross-sectional view of the fluid cooling device of the device illustrated in FIG. 6A.

FIG. 7A illustrates a preferred configuration of a polishing plate according to the present invention and a corresponding footprint of the polishing plate on a substrate surface.

FIG. 7B illustrates another form of polishing plate and drum type roller footprint that may be employed with the present invention.

FIG. 7C illustrates another form of polishing plate and drum type roller footprint that may be employed with the present invention.

FIG. 8 is a rear view of a portion of the apparatus of FIG. 4, wherein a voltage is applied between a rotating substrate and a pair of stationary polishing plates that presses a polishing tape against each surface on both sides of the substrate. An example of an electrical connection for making the connection will be described.

9 is a longitudinal sectional view of a part of the device illustrated in FIG. 8;

FIG. 10 is a perspective view of a brush assembly for providing electrical contact to a rotating shaft that is part of the device illustrated in FIG.

FIG. 11 is a computer control circuit for controlling an AC voltage source applied between a substrate and a stationary polishing plate with AC constant current control for use in an electrochemical mechanical polishing apparatus according to the present invention. An example is shown below.

FIG. 12 is a diagram illustrating a part of an orbital motion polishing apparatus according to the present invention.

[Description of Reference Numerals] 20 substrate 22 polishing pad 24 polishing platen 28 slurry 30 nozzle 32 power supply

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Roger Oh. Williams United States California 94539, Fremont, Ranch Higuera Load 47267 F-term (reference) 3C058 AA05 AA07 AA09 AA12 AB01 AC04 BA08 BA09 BB02 BB06 CB01 CB03 DA06 DA12

Claims (34)

[Claims] 1. An apparatus for polishing a substrate for use in a magnetic recording and storage system, comprising: a polishing medium; means for moving the substrate to polish the medium relative to each other; Means for polishing the medium together in the presence of the slurry to chemically and mechanically polish the surface of the substrate; and generating an electric current between the substrate and the conductive member to electrically connect the substrate surface. And a voltage source for polishing. 2. The apparatus of claim 1, wherein said voltage source comprises one of a DC voltage source and an AC RF voltage source. 3. The apparatus according to claim 2, wherein said conductive member is stationary and connected to said voltage source, said substrate is movable by said movement means, and said device slidably engages said movement means to move said substrate. The apparatus of claim 2, further comprising an electrical contact for connecting to the voltage source. 4. The apparatus of claim 3, wherein said conductive member comprises a plate mounted on said biasing means for pressing said polishing medium against said substrate surface. 5. The apparatus according to claim 4, wherein said movement means rotates said substrate with respect to said plate, said plate being reproducible and configured to provide a uniform current density on said surface of said substrate. Equipment. 6. The apparatus of claim 5, wherein said plate is wedge-shaped and all points on said substrate are dimensioned to carry an equal current for a given period. 7. The polishing medium comprises a linear tape, and the urging means includes means for urging a conductive member to engage the tape and press the tape against the surface of the substrate. 2. The apparatus of claim 1, wherein the means for moving comprises means for rotating the substrate with respect to the tape. 8. The tape according to claim 7, wherein the tape is conductive, the electrolytic slurry is conductive, and a current flows between the substrate and the conductive member via the tape. apparatus. 9. The method according to claim 1, wherein the electrolytic slurry is sulfuric acid, chromic acid,
9. The apparatus of claim 8, comprising an acid selected from the group consisting of and orthophosphoric acid, and a salt selected from the group consisting of ammonium sulfate, potassium chloride, potassium permanganate, and nickel sulfate. 10. The apparatus according to claim 9, wherein said substrate surface is made of metal and said slurry is a sludge slurry containing a saturated solution of said metal. 11. The apparatus of claim 1, wherein the voltage source comprises an adjustable constant DC power supply, the substrate is connected to a positive terminal of the power supply, and the conductive member is connected to a negative terminal power supply. 12. The apparatus of claim 1, wherein said voltage source comprises means for adjusting a current in response to a computer control signal. 13. The polishing medium according to claim 1, wherein said polishing medium comprises a linear tape, said biasing means comprising a roller engaging said tape, and means for pressing said roller and tape against a surface of said substrate. An apparatus according to claim 1. 14. The roller comprises the conductive member,
14. The apparatus of claim 13, wherein the rollers are formed from a conductive material and are rotatably supported on a conductive shaft by conductive bearings. 15. The conductive member comprises an electrode disposed between the tape and the substrate surface, wherein the electrode engages the tape and is disposed in the flow of the electrolytic slurry. Apparatus according to claim 13. 16. An apparatus for polishing a substrate used in a magnetic recording system, comprising: means for rotating the substrate; means for advancing a linear polishing tape on both sides of the substrate; Means for urging the polishing tape against the surface to mechanically polish the surface; means for introducing an electrolytic slurry between the substrate and the polishing tape; and supplying a voltage between the substrate and the electrode. And voltage source means for causing a current to flow between the substrate and the electrode via an electrolytic slurry. 17. The tape of claim 16, wherein the tape is conductive, the electrodes are positioned to engage the tape, and current flows between the substrate and the electrodes through the tape. An apparatus according to claim 1. 18. The apparatus of claim 18, wherein the electrodes comprise plates disposed on opposite sides of the substrate, and the biasing means comprises means for pressing the plates together to press the tape against the substrate surface. Item 16. The device according to item 16. 19. The voltage supply means comprises a DC constant current control source, wherein the tape is porous and allows current to flow between the plate and the substrate through the tape. Item 19. The apparatus according to Item 18. 20. The apparatus of claim 18, wherein said means for providing a power supply voltage comprises an AC constant current source. 21. The apparatus according to claim 16, further comprising cooling means for cooling said substrate and said rotating means to maintain the temperature of said substrate and said rotating means within a predetermined temperature range. 22. The apparatus of claim 21, wherein said rotating means comprises a rotating spindle and said cooling means comprises means for directing a cooling liquid onto said spindle and said substrate. 23. The voltage supply means includes a first power supply and a second power supply, each power supply being connected to one of the plates and the substrate rotating means, each of the power supplies being independently controllable. 19. The apparatus of claim 18, wherein the current is controlled for each side of the substrate. 24. The power supply comprises an AC source having means for adjusting a current in response to a computer control signal.
An apparatus according to claim 22. 25. The apparatus of claim 23, wherein the plate is shaped and dimensioned to provide a uniform predetermined current density across the surface of the substrate. 26. An apparatus for polishing a substrate for use in a magnetic recording system, comprising: an orbital motion polisher, wherein the orbital motion polisher includes a fixed polishing platen and a substrate carrier movable with respect to the fixed platen. Means for biasing the substrate into engagement with a polishing medium positioned on the stationary polishing platen; and moving the substrate in orbital motion on the polishing medium. Orbital motion polisher having means, means for introducing an electrolytic conductive slurry between the substrate and the polishing medium, and a voltage source connected to the polishing platen and the substrate carrier, wherein the substrate and A current flows between the polishing platen and the surface of the substrate at the same time as a chemical mechanical polishing step of the substrate surface due to relative movement between the substrate and the polishing medium. A voltage source adapted to electropolish the surface. 27. The voltage source, comprising: an AC constant-amplitude current source;
27. The apparatus of claim 26, further comprising: means for controlling the current source to supply a predetermined current between the substrate and the platen. 28. The apparatus of claim 27, wherein said AC source comprises means for adjusting current in response to a computer control signal. 29. The AC constant current source may be 1 kHz to 50
28. The device of claim 27, having an output frequency in the range of MHz. 30. A method of polishing a substrate for use in a magnetic recording system, comprising: providing a polishing medium; and energizing the substrate and the medium together in the presence of an electrolytic slurry. Moving the substrate with respect to the polishing medium to chemically and mechanically polish the surface of the substrate; and allowing a current to flow through the slurry between the substrate and the conductive member, and simultaneously using the Removing material from a surface and electropolishing the substrate surface while the substrate surface is being chemically and mechanically polished. 31. The means for causing a current to flow includes:
31. The method of claim 30, including causing a uniform current density to flow between the substrate surface and the conductive member. 32. The polishing medium comprises a first linear tape and a second linear tape having an abrasive coating thereon, wherein the tape is disposed on both sides of the substrate and moves on a side of the substrate surface; The tape is biased by an interacting plate that is biased together to engage the substrate surface and allow the current to flow, wherein a voltage is applied between each of the plates and the rotating substrate. 31. The method of claim 30, comprising applying. 33. The voltage according to claim 32, wherein the voltage comprises an AC constant amplitude current source that is controlled to produce a predetermined current.
An apparatus according to claim 1. 34. The method further comprising cooling the substrate during polishing to maintain a substantially constant temperature.
A method according to claim 30.